[s-cars] BBK issue
Theodore Chen
tedebearp at yahoo.com
Mon Jul 7 15:29:54 PDT 2008
ferodo DS2500? aren't those club race pads? streetable, but noisy.
if you have a set of street pads lying around, i'd try those. swapping the pads is pretty quick and may solve your problem. while you're at it, you might want to apply some antiseize to the edges of the pad backing plates where they contact the locating pins.
----- Original Message ----
From: jpb3 <jpburns3 at gmail.com>
To: "s-car-list at audifans.com" <s-car-list at audifans.com>
Cc: jpb3wvu at yahoo.com
Sent: Monday, July 7, 2008 7:34:17 AM
Subject: [s-cars] BBK issue
Hi Randy, hope you had a good rally and better luck with your tandem
than with the S! I am going to copy the S car list with our train of
correspondence. (If any lister wants to read through from the bottom
up any feedback or advice is greatly appreciated!)
This problem we are both dealing with seems to have gotten somewhat
worse for me over the holiday. I was running the OEM Avus 16" wheels
which have very small clearance with the caliper so I was hoping that
perhaps some sort of resonancy was happening between that rim and the
caliper when the caliper warmed and expanded a slight bit. Note I
have been using "hoping" far too much in our conversations! I put my
17" Bolero's on this weekend with mucho clearance but as you know it
makes no difference! As I have said before if it was not for the
direct correlation with the brake pedal and the noise I would believe
that the wheel bearing is bad, but seeing how that if you just barely
tap the brake pedal the noise goes away momentarily (until you let
off) I cannot bring myself to that conclusion, yet.
So that we are on the same page I will list what is on my car and when
the noise started happening. I made a close visual inspection of
everything when I did the wheel swap this weekend and nothing looks
out of place, nothing looks like it should be making this noise!
95 S6, 928GTS calipers from Benson Porsche, brand new.
OEM RS2 caliper brackets from VAG Parts UK, not machined.
A8 (323mm?) Brembo rotors, brand new from PartsQuick.
Ferodo DS2500 pads, brand new.
Paragon braided hoses, banjo fitting.
Porsche OEM caliper bolts.
*034 bracket bolts* (note, these are standard metric head Vs. the OEM
Hex head bracket bolts I have seen elsewhere)
Super Blue, pressure bled.
My braking system did not make any noise (other than pad squeal) for
the first hundred or so miles. I bedded everything in properly
according to Mov-it instructions on their website. As I have stated
before my brakes immediately started making this groaning noise after
a very hard stop to avoid a collision with someone who pulled out in
front of me. At the time I thought I may have bended something
(bracket?) when I did that stop though that doesn't make sense. I
drove another 10 miles and pulled over and inspected b/c I thought
that I was rubbing the caliper against the wheel or something of that
nature. Nothing looked amiss. Noise then became intermittent and not
too bad, only occasionally making itself known. Turning left induced
the noise, turning right quieted it or if I tapped my brakes it would
stop for awhile. It was only doing this for about two weeks before I
was hit and my car than sat at a body shop for 5 weeks............that
about brings us up to present.
On the way home from body shop the noise returned, only this time
worse. (More grinding sound, vibrations in the steering wheel.) Put
my 17" Bolero's on and now the noise is present every time I drive.
It use to take some driving time (10-15 minutes) before the noise
would appear, this has been reduced dramatically to about 3-5 minutes
as evidenced on the way to work this morning. It is now very loud and
once it starts the only thing that makes it stop is turning right or
tapping the brakes, and only momentarily when performing one of these
actions. Suspension deflection also seems to have an impact. I live
in very rolling terrain, with lots of hills and dips. When the
suspension loads up the noise is there, when it unloads (cresting a
hill) it subsides somewhat for a second.
ALL of the above sounds like a wheel bearing to me. HOWEVER, there is
no play whatsoever when I have the wheel off the ground and do the
Up/down, forward/back check for play. Also, why would even the
slightest (resting foot) on the brake pedal have any impact on the
noise if it was a wheel bearing? I can quiet the noise completely if
I ride the pedal.
I am at a loss and await to hear if your swapping of the rotors and
brackets makes any difference. If it does I am going to order new
slotted rotors from Apikol but I just can't see the rotors being the
issue. I re-read your original email and the theory of brake fluid
expansion leading to pad dragging is interesting but my fluid is fresh
and blue, no old left in the system and pressure bled. Noise is
getting progressively worse which again points to a wheel bearing.
But is doesn't feel like a wheel bearing, it definitely feels like
something is going on with the braking system on the passenger side.
Thanks,
John
----- Original Message ----
From: "McCall, Randy" <rmccall at nexant.com>
To: jpb3 <jpb3wvu at yahoo.com>
Sent: Friday, July 4, 2008 6:35:09 PM
Subject: RE: posts on groaning big brakes
Yep, if I tap the brakes the noise stops momentarily (until, of course
I let off the brakes...)
One thing I'm going to try (before I pronounce it the caliper), is to
swap the brake brackets and rotors from side to side and see if the
noise also migrates. Mine made no noise prior to installation of the
new brackets, A8 rotors (in place of the slotted ECS 314 mm rotors)
and brake pads. I just don't believe its brake pads, and I also don't
hold a strong opinion on the caliper sticking. Would have done so
before is my thought.
Have company for the weekend and a tandem (bicycle) rally this weekend
in McMinville, so not until the beginning of the week...
-Randy
From: jpb3 [mailto:jpb3wvu at yahoo.com]
Sent: Friday, July 04, 2008 8:48 AM
To: McCall, Randy
Subject: Re: posts on groaning big brakes
Hi Randy,
Looks like you have covered your bases there with the pads. Forgot to
mention that I have the factory vibration dampers installed as well
and have since the initial install. My brakes never did this prior to
a ultra hard stop (to avoid a T collision on a 2 lane rd).
Mine is also the right side that sings. If you chamfered the pads and
greased everything with no results I am not going to go down that
path. The scenario about the hanging piston seems right to me, though
my calipers are brand new so that is discomforting. When the brakes
start singing if I just barely tap the brakes it will interrupt the
noise, does yours do this as well? If it wasn't for this fact I would
point to the wheel bearing as that is what it sounds like but I know
it cannot be that b/c of the complete correlation with the brake
pedal.
I am going to look and perhaps try some things today, will let you
know if I come across anything.
John
----- Original Message ----
From: "McCall, Randy" <rmccall at nexant.com>
To: jpb3 <jpb3wvu at yahoo.com>
Sent: Friday, July 4, 2008 9:01:17 AM
Subject: RE: posts on groaning big brakes
Hey John,
I chamfered the brake pads, and put on the OEM vibration dampers last
week. I also lightly lubed the edge of the pad where the metal
contacts the caliper with a special silicon caliper grease. (also
checked the axle bolt). No go.... Still sings like a canary (one
note though) after the brakes are warm. I talked with 034 who sold me
the brackets and bolts - they had no ideas; talked with Scott Mockry
at SJM; same story. He thought that maybe one of the calipers wasn't
retracting - seems as though mine is the right side that is singing.
So not answers yet on the resolution, and sounds like there are at
least two of us with the problem! Do you have the Euro A8 rotors ie,
non-slotted, non-drilled?
My previous 314mm rotors from ECS were slotted, and made no noise with
these calipers and same brake pads.
-Randy
From: jpb3 [mailto:jpb3wvu at yahoo.com]
Sent: Friday, July 04, 2008 5:50 AM
To: McCall, Randy
Subject: Re: posts on groaning big brakes
Hi Randy,
Thanks for your insights. I just got my car back from the body shop
yesterday and on the way home the brakes started singing like they
never have before! So much for my axle bolt theory (that was a bit of
a stretch to begin with). It definitely sounds as though it is a
harmonic resonance from the brakes, if I just lightly tap the brakes
it stops completely. As soon as I lift my foot off the pedal it
begins again. It only happens after the braking materials are warm as
well. Never heard it in the first few miles of the day when
everything is still cold.
This points to the caliper assembly and not much else IMO. I am going
to throw my summer wheels on today and will make a close inspection of
the front left caliper assembly. Is that the same side yours is
making noise as well?
Any updates on your progress solving this noise?
Thanks,
John
----- Original Message ----
From: "McCall, Randy" <rmccall at nexant.com>
To: jpb3 <jpb3wvu at yahoo.com>
Sent: Monday, June 23, 2008 9:18:15 AM
Subject: RE: posts on groaning big brakes
Hi John,
Thanks for the detailed reply. Sorry to hear about the accident -
I've got another 95.5 S6 in my woodshop still being dismantled after
getting rear-ended at about 50mph.....Engine went to Mahoney, Tranny
and ECU to Canada, and lots of other parts have been scattered across
the country.
And thanks for the tip on the axle bolt - I do have the torque wrench
big enough to check that, and that's an easy one to try. I ordered
the anti-vibration dampers this weekend from SJM, so I'll throw those
in whenever they arrive also. I don't think the wheel bearing is a
problem with this car, but you never know. In my case, before I
retrofitted the new brackets and rotors and went from the ECS stage II
BBK to the full RS2 brackets, 323 rotors, and 928GTS calipers, there
was no singing brakes! The old rotors were the slotted ECS rotors
(314mm I think).
The noise now isn't so much a groan as it is a single pitch hum - a
resonance type noise from rubbing. It happens in straight line, but
also increases on left hand turns; that could point to the loose axle
bolt... I'll sure as heck try the easy stuff like axle bolt torque
first!
I'll let you know the outcome on my various remedies...
Thanks,
-Randy
From: jpb3 [mailto:jpb3wvu at yahoo.com]
Sent: Monday, June 23, 2008 5:16 AM
To: McCall, Randy
Subject: Re: posts on groaning big brakes
Hi Randy,
Unfortunately my car was rear ended and has been at a body shop for
about a month now and I did not completely solve the "groaning" issue
with the brakes before it went in. I originally thought it was a
wheel bearing, as the noise originally appeared after I did a hard
stop to avoid a collision. This was from about 75mph to
lock-antilock. I thought that since I had just installed the BBK
that perhaps this braking event might have put enough force on the
wheel bearing that it made a weak or almost ready to fail bearing
apparent.
The problem was that there was literally no movement of the wheel when
I tested it while it was jacked up off the ground. No side to side or
top to bottom movement whatsoever. I have had bead wheel bearings
before and usually you can almost always feel the bearing going out
but tugging on the wheel in all directions.
What did happen was I had to order a special 17mm hex socket for the
Wheel bearing R&R for the axle bolt. To my surprise when I went to
loosen the axle bolt I found it already loose! It wasn't finger loose
but pretty close to it. This was odd since the required torque for
that monster is somthing like 168 ft/lb! Since I do not have a torque
wrench that goes that high I took my 3/4 drive ratchet and a small
section of pipe and tightened it as much as I thought I should. The
"groaning" all but dissapeared! It has not completely gone away but
was infrequent and not any where near as loud or continuos as before.
In fact it has probably only happened 2-3 times since I tightend that
axle bolt and only for a second or two. In my opinion it probably
isn't quite tight enough but I will fix that once I get my car back as
I have large torque wrench now and am curious as to how tight that
bolt really is. I probably only had it a week or so in this condition
before I was hit so my results are not conclusive.
So..check that axle bolt first and see if it is tight. I am
interested to know. If yours is tightend to spec it I would then take
the wheel and brake disc off and check that guard behind the disc,
just to make sure it is not the culprit. ( i dont think it will be )
I am not yet convinced that it is NOT a wheel bearing issue, though as
I said I all but eliminated the noise by tightening up my axle bolt.
Let me know if your is loose as well.
John
----- Original Message ----
From: "McCall, Randy" <rmccall at nexant.com>
To: jpb3wvu at yahoo.com
Sent: Saturday, June 21, 2008 12:59:59 PM
Subject: RE: posts on groaning big brakes
Searching the archives, I saw your post on AW from March of this year
regarding your PS groan after installing a BBK. I had an existing BBK
on my 95.5S6A when I bought the car, found out when I went to change
the pads and rotors that it was a Stage II ECS kit with smaller
rotors... Put in new machined RS2 brackets from 034 (for corrected
side-side rotor position)and reinstalled the new 323 rotors, stock
Textar Porsche pads. Since that time I have been getting a "groan"
that happens a lot like what you described. Hard to tell if its from
one side or the other, but it is fine until you drive 10 minutes or
so, then you can hear it on straight line driving, and even feel it a
bit in the steering wheel.
I was thinking this was a pad dragging after brake fluid warmed and
perhaps a small bit of air in the caliper, so I recently power-bled
all the corners and flushed the Super Blue fluid (came out clean); the
car came without pad dampers, so I've ordered those to see if that
might help.
Question after this long explanation is: was your problem a wheel
bearing, or do the brakes continue to "sing" at a kind of resonant
frequency like mine now are. Not a squeal, but a light groan like you
described.
Thanks
-Randy
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